1. Technical Field
The invention relates to a spot welding system and a spot welding method.
2. Description of Related Art
In a spot welding gun in which a workpiece to be welded is held between a movable electrode tip and a fixed electrode tip to be welded, when the workpiece to be welded is pressed between the movable electrode tip and the fixed electrode tip, a gun arm which supports the movable electrode tip and the fixed electrode tip is elastically displaced. Due to such elastic displacement of the gun arm, deterioration, etc., in welding accuracy may occur.
Conventionally, a technique of estimating an elastic displacement of a gun arm during pressing of a workpiece to be welded by recording the relationship between a pressing force applied to the workpiece to be welded and the amount of elastic displacement of the gun arm as a reference data in advance and by basing on the reference data is known (see, for example, Japanese Patent Publication No. 06-155036 and Japanese Patent Publication No. 08-206846.
The degree of elastic displacement of a gun arm differs from one gun arm to another. In a conventional system, when estimating the amount of elastic displacement of a gun arm by evenly applying a reference data, it is not possible to accurately calculate the amount of elastic displacement for individual gun arms. Further, in a conventional system, a troublesome work will be necessary when trying to obtain reference data for each gun arm before welding in order to improve accuracy of the amount of elastic displacement to be calculated.